7-i

CHAPTER 7. ENERGY USE ANALYSIS

TABLE OF CONTENTS

7.1 INTRODUCTION ........................................................................................................... 7-1

7.2 BUILDING SAMPLE ..................................................................................................... 7-2

7.3 COMMERCIAL PACKAGED BOILER ENERGY CONSUMPTION......................... 7-7

7.3.2 Space-Heating Fuel Consumption ................................................................................... 7-8

7.3.2.2 Determination of Space-Heating Burner Operating Hours (BOHSH) ............ 7-9

7.3.2.3 Determination of Equipment Sizing ............................................................ 7-11

7.3.3 Water-Heating Energy Consumption............................................................................. 7-12

7.3.4 Electricity Consumption ................................................................................................ 7-13

7.4 SUMMARY OF ENERGY USE RESULTS................................................................. 7-13

LIST OF TABLES

Table 7.1.1 Commercial Packaged Boiler Equipment Classes Analyzed............................... 7-1

Table 7.2.1 Selection of CBECS 2003 Records for Commercial Packaged Boilers.............. 7-5

Table 7.2.2 Selection of RECS 2009 Records for Commercial Packaged Boilers................. 7-6

Table 7.2.3 Fractions of Commercial Boilers in New Construction Buildings based on 

the Shipment Model Developed in the NIA (Commercial Sample).................... 7-7

Table 7.4.1 Average Annual Energy Consumption and Savings for Commercial 

Packaged Boilers................................................................................................ 7-14

LIST OF FIGURES

Figure 7.3.1 Space-Heating Energy Use Methodology............................................................ 7-8
7-1

CHAPTER 7. ENERGY USE ANALYSIS

7.1 INTRODUCTION

The purpose of the energy use analysis is to determine the annual energy consumption of 

commercial packaged boilers in use in the United States and to assess the energy savings 

potential of increases in efficiency (thermal efficiency (TE) or combustion efficiency (CE)). In 

contrast to the commercial packaged boiler test procedure under Title 10 of the Code of Federal 

Regulations, Part 431, which uses fixed operating conditions in a laboratory setting, the energy 

use analysis for commercial packaged boilers seeks to estimate the range of energy consumption 

of the equipment in the field. The U.S. Department of Energy (DOE) estimates the annual energy 

consumption of such boilers at specified energy efficiency levels across a range of climate zones,

building characteristics, and space and water heating applications.

For the calculation of the energy consumed by commercial packaged boilers, DOE 

considers the energy use associated with providing space heating and water heating in either 

commercial or residential buildings. Space heating applications for commercial packaged boilers 

include forced air using fan coils or central air handlers and radiant heating (in-floor, radiant 

panels, radiators, baseboard). Water heating applications for commercial packaged boilers 

include indirect water heating, combination equipment, and tankless coil-type. The energy use 

analysis provides estimates of the distribution of annual energy consumption for boilers at each

efficiency standard level considered.

DOE develops energy consumption estimates for the key equipment classes listed in 

Table 7.1.1. The boilers analyzed utilize gas or oil fuel for heating water or steam and the 

associated electric energy to power a water pump, a draft inducer, an igniter, and other auxiliary 

equipment. 

Table 7.1.1 Commercial Packaged Boiler Equipment Classes Analyzed

Heating 

Medium Subcategory Size category (input) Draft Type Abbreviation

Hot Water Gas-fired ≥300,000 Btu/hr and ≤2,500,000 Btu/hr Natural Draft SGNDHW

Hot Water Gas-fired >2,500,000 Btu/hr Natural Draft LGNDHW

Hot Water Oil-fired ≥300,000 Btu/hr and ≤2,500,000 Btu/hr Natural Draft SONDHW

Hot Water Oil-fired >2,500,000 Btu/hr Natural Draft LONDHW

Steam Gas-fired ≥300,000 Btu/hr and ≤2,500,000 Btu/hr Natural Draft SGNDST

Steam Gas-fired >2,500,000 Btu/hr Natural Draft LGNDST

Steam Oil-fired ≥300,000 Btu/hr and ≤2,500,000 Btu/hr Natural Draft SONDST

Steam Oil-fired >2,500,000 Btu/hr Natural Draft LONDST

Hot Water Gas-fired ≥300,000 Btu/hr and ≤2,500,000 Btu/hr Mechanical Draft SGMDHW

Hot Water Gas-fired >2,500,000 Btu/hr Mechanical Draft LGMDHW

Hot Water Oil-fired ≥300,000 Btu/hr and ≤2,500,000 Btu/hr Mechanical Draft SOMDHW

Hot Water Oil-fired >2,500,000 Btu/hr Mechanical Draft LOMDHW

Steam Gas-fired ≥300,000 Btu/hr and ≤2,500,000 Btu/hr Mechanical Draft SGMDST

Steam Gas-fired >2,500,000 Btu/hr Mechanical Draft LGMDST

Steam Oil-fired ≥300,000 Btu/hr and ≤2,500,000 Btu/hr Mechanical Draft SOMDST

Steam Oil-fired >2,500,000 Btu/hr Mechanical Draft LOMDST
7-2

DOE estimates the energy consumption of commercial packaged boilers in commercial 

buildings and housing units by developing a building sample for each of the 16 equipment

classes based on the Energy Information Administration’s (EIA) 2003 Commercial Building 

Energy Consumption Survey (CBECS 2003) and EIA’s 2009 Residential Energy Consumption 

Survey (RECS 2009).

1, 2 These are the latest available surveys for commercial and residential

buildings.a This sample is further described in section 7.2.

DOE used CBECS 2003- or RECS 2009-reported heating energy consumption (based on 

the existing heating system) to calculate the space-heating load of each building. The heating 

load represents the amount of heating required to keep a building comfortable throughout an 

average year. In buildings where DOE finds that the boiler also serves hot water heating needs, 

DOE uses the CBECS 2003- or RECS 2009- reported water-heating energy (based on the 

existing water heating system) to calculate the water heating load of each building.

DOE assigns the energy efficiency of existing systems based on a historical distribution 

of energy efficiency for boilers by equipment class. In addition, DOE makes adjustments based 

on historical weather data, average estimated return water temperature, projections of shell 

efficiency and building square footage, and for buildings that had secondary heating equipment 

that used the same fuel as the boiler. To complete the analysis, DOE calculates the energy 

consumption of alternative (more energy-efficient) equipment if they replaced existing systems 

in each commercial building or housing unit.

7.2 BUILDING SAMPLE

DOE’s determination of the annual energy use of commercial packaged boilers relies on 

data from CBECS 2003 and RECS 2009.

1, 2 CBECS 2003 includes energy-related data from 

5,215 buildings representing 4.9 million buildings. RECS 2009 includes energy-related data from 

12,083 housing units that represent almost 113.6 million households.

The subset CBECS 2003 or RECS 2009 records used in the analysis meet all the 

following criteria:

• use a boiler as the main or secondary source of heat;

• use a heating fuel that is natural gas (not including liquid petroleum gas (LPG)) or fuel 

oil; and

• have a heating energy consumption greater than zero.

DOE disaggregates EIA’s CBECS 2003- and RECS 2009-derived commercial packaged 

boiler subset into further subsets based on the boiler fuel, size, heating medium (steam or hot 

water), and draft type (natural or mechanical draft). These subsets are designed to isolate the

buildings that are equipped with each of the different equipment classes (Table 7.2.1 for 

 a EIA is currently working on the 2013 version of RECS, which is not expected to be available until 2015. 

Additionally, EIA determined that the 2007 Commercial Buildings Energy Consumption Survey did not yield valid 

statistical estimates of building counts, energy characteristics, consumption and expenditures and therefore did not 

release the majority of the data tables and public use files.
7-3

commercial applications and Table 7.2.2 for residential applications). To sample between the 

commercial and residential samples, DOE uses the square footage weighted fractions of each 

equipment class sample. The new construction sample is based on the same selection algorithms 

as the replacement sample but only includes buildings built after 1990, which DOE believes 

would have more similar building characteristics to the new construction buildings in 2019 (e.g.

building insulation, regional distribution of the buildings, and so forth.).

To disaggregate between large and small equipment classes, DOE develops a scheme to 

determine the size of the boiler installed in the building. For both the commercial and residential 

samples, the sizing of the equipment installed in the building is determined from the heated 

square footage of the building and on a heating load per floor area of 30 Btu/h/sqft, and is 

adjusted to account for an oversize factor of 1.1, the efficiency of the equipment (which is based 

on the construction year), and the outdoor design temperature corresponding to the weather 

location of the building. 

The number of boilers for both the commercial and residential samples are determined 

using the total sizing of the equipment:3

1) when the total sizing is larger than 7.11b MMBtu/hr, the number of boilers is equal to the 

total sizing divided by 6.7c MMBtu/hr, 

2) when the total sizing is below 7.11 MMBtu/h but larger than 2.5d MMBtu/h, the number 

of boilers is equal to the total sizing divided by 4.4e MMBtu/hr, 

3) when the total sizing is below 2.5 MMBtu/h, the number of boilers is equal to the total 

sizing divided by 1.1f MMBtu/hr, 

The sample is disaggregated by boiler size based on the sizing of all equipment and on 

the number of boilers in each building. 

Both the replacement and the new construction sample are disaggregated by natural and 

mechanical draft by applying fractions of natural and mechanical draft data based on model data 

extracted from the Air-Conditioning, Heating, and Refrigeration Institute (AHRI) Directory of

Certified Product Performance.

3

Steam boilers are assumed to be installed in 14 percent of buildings built before 1970 and

in 0 percent of buildings built after 1970.

4

 b 7.11 MMBtu/hr, is the 90th percentile of the input capacity of the large commercial packaged boilers (above 2.5 

MMBtu/hr) derived from the CBECS-2003-based commercial sample that was determined for this analysis (all 

fuels, heating mediums and draft types) 

c 6.7 MMBtu/hr, is the 90th percentile of the input capacity of large commercial packaged boilers (above 2.5 

MMBtu/hr) found in the AHRI directory (all fuels, heating mediums and draft types)

d 2.5 MMBtu/hr is the limit in terms of input capacity, above which a boiler is considered large

e 4.4 MMBtu/hr, is the average input capacity of large commercial packaged boilers (above 2.5 MMBtu/hr) found in 

the AHRI directory (all fuels, heating mediums and draft types)

f 1.1 MMBtu/hr, is the average input capacity of small commercial packaged boilers (below 2.5 MMBtu/hr) found in 

the AHRI directory (all fuels, heating mediums and draft types)
7-4

Commercial packaged boilers are considered in residential applications when the total 

heated square footage of the building (equal to the heated square footage of each unit multiplied 

by the number of units in the building), is larger than 10,000 square feet (usually multifamily 

buildings). 

The CBECS 2003 and RECS 2009 weighting indicates how commonly each commercial 

building or household configuration occurs on the national level, in 2003 and 2009, respectively. 

DOE adjusted EIA’s weightings for CBECS 2003 and RECS 2009 buildings to adjust for

buildings with multiple boilers. Appendix 7-A presents the variables included and their 

definitions, as well as further information about the derivation of the building samples, the 

adjustments to the boiler weights, and sampling fractions for each of the four samples 

commercial and residential, both disaggregated between new construction and replacement.
7-5

Table 7.2.1 Selection of CBECS 2003 Records for Commercial Packaged Boilers 

Equipment Class No. of 

Records

CBECS 

2003 DOE 2019

Fraction

of New 

Construction Number of 

Buildings

Number of 

Boilers

Natural Draft Gas-Fired Hot Water Commercial Packaged 

Boiler ≥300,000 Btu/hr and ≤2,500,000 Btu/hr 482 10847 15619 18%

Natural Draft Gas-Fired Hot Water Commercial Packaged 

Boiler >2,500,000 Btu/hr 480 318 548 24%

Natural Draft Oil-Fired Hot Water Commercial Packaged 

Boiler ≥300,000 Btu/hr and ≤2,500,000 Btu/hr 73 8993 11218 26%

Natural Draft Oil-Fired Hot Water Commercial Packaged 

Boiler >2,500,000 Btu/hr 142 5479 8922 16%

Natural Draft Gas-Fired Steam Commercial Packaged Boiler 

≥300,000 Btu/hr and ≤2,500,000 Btu/hr 266 40890 55621 0%

Natural Draft Gas-Fired Steam Commercial Packaged Boiler 

>2,500,000 Btu/hr 225 3986 6181 0%

Natural Draft Oil-Fired Steam Commercial Packaged Boiler 

≥300,000 Btu/hr and ≤2,500,000 Btu/hr 50 1795 2450 0%

Natural Draft Oil-Fired Steam Commercial Packaged Boiler 

>2,500,000 Btu/hr 79 2292 3752 0%

Mechanical Draft Gas-Fired Hot Water Commercial 

Packaged Boiler ≥300,000 Btu/hr and ≤2,500,000 Btu/hr 482 130409 187777 18%

Mechanical Draft Gas-Fired Hot Water Commercial 

Packaged Boiler >2,500,000 Btu/hr 480 38217 65777 24%

Mechanical Draft Oil-Fired Hot Water Commercial Packaged 

Boiler ≥300,000 Btu/hr and ≤2,500,000 Btu/hr 73 20542 25625 26%

Mechanical Draft Oil-Fired Hot Water Commercial Packaged 

Boiler >2,500,000 Btu/hr 142 5479 8922 16%

Mechanical Draft Gas-Fired Steam Commercial Packaged 

Boiler ≥300,000 Btu/hr and ≤2,500,000 Btu/hr 266 7638 10390 0%

Mechanical Draft Gas-Fired Steam Commercial Packaged 

Boiler >2,500,000 Btu/hr 225 5983 9278 0%

Mechanical Draft Oil-Fired Steam Commercial Packaged 

Boiler ≥300,000 Btu/hr and ≤2,500,000 Btu/hr 50 7738 10559 0%

Mechanical Draft Oil-Fired Steam Commercial Packaged 

Boiler >2,500,000 Btu/hr 79 2292 3752 0%
7-6

Table 7.2.2 Selection of RECS 2009 Records for Commercial Packaged Boilers 

Equipment Class No. of 

Records

RECS

2009

DOE 

2019 Fraction

of New 

Construction

Number 

of 

Buildings

Number 

of 

Boilers

Natural Draft Gas-Fired Hot Water Commercial Packaged 

Boiler ≥300,000 Btu/hr and ≤2,500,000 Btu/hr 125 2585 2963 7%

Natural Draft Gas-Fired Hot Water Commercial Packaged 

Boiler >2,500,000 Btu/hr 29 15 18 16%

Natural Draft Oil-Fired Hot Water Commercial Packaged 

Boiler ≥300,000 Btu/hr and ≤2,500,000 Btu/hr 69 4931 5743 8%

Natural Draft Oil-Fired Hot Water Commercial Packaged 

Boiler >2,500,000 Btu/hr 12 266 327 12%

Natural Draft Gas-Fired Steam Commercial Packaged Boiler 

≥300,000 Btu/hr and ≤2,500,000 Btu/hr 79 3144 3548 0%

Natural Draft Gas-Fired Steam Commercial Packaged Boiler 

>2,500,000 Btu/hr 13 55 68 0%

Natural Draft Oil-Fired Steam Commercial Packaged Boiler 

≥300,000 Btu/hr and ≤2,500,000 Btu/hr 57 431 500 0%

Natural Draft Oil-Fired Steam Commercial Packaged Boiler 

>2,500,000 Btu/hr 10 35 42 0%

Mechanical Draft Gas-Fired Hot Water Commercial 

Packaged Boiler ≥300,000 Btu/hr and ≤2,500,000 Btu/hr 125 31082 35621 7%

Mechanical Draft Gas-Fired Hot Water Commercial 

Packaged Boiler >2,500,000 Btu/hr 29 1764 2129 16%

Mechanical Draft Oil-Fired Hot Water Commercial Packaged 

Boiler ≥300,000 Btu/hr and ≤2,500,000 Btu/hr 69 11264 13119 8%

Mechanical Draft Oil-Fired Hot Water Commercial Packaged 

Boiler >2,500,000 Btu/hr 12 266 327 12%

Mechanical Draft Gas-Fired Steam Commercial Packaged 

Boiler ≥300,000 Btu/hr and ≤2,500,000 Btu/hr 79 587 663 0%

Mechanical Draft Gas-Fired Steam Commercial Packaged 

Boiler >2,500,000 Btu/hr 13 82 103 0%

Mechanical Draft Oil-Fired Steam Commercial Packaged 

Boiler ≥300,000 Btu/hr and ≤2,500,000 Btu/hr 57 1857 2155 0%

Mechanical Draft Oil-Fired Steam Commercial Packaged 

Boiler >2,500,000 Btu/hr 10 35 42 0%

To sample between the new construction and replacement markets, DOE uses the 

fractions derived in the National Impact Analysis (NIA) of commercial packaged boilers shipped 

to new and replacement construction (see Table 7.2.3).
7-7

Table 7.2.3 Fractions of Commercial Boilers in New Construction Buildings based 

on the Shipment Model Developed in the NIA (Commercial Sample)

Equipment Class New Construction 

Fractions

Natural Draft Gas-Fired Hot Water Commercial Packaged Boiler ≥300,000 Btu/hr and 

≤2,500,000 Btu/hr 12%

Natural Draft Gas-Fired Hot Water Commercial Packaged Boiler >2,500,000 Btu/hr 1%

Natural Draft Oil-Fired Hot Water Commercial Packaged Boiler ≥300,000 Btu/hr and 

≤2,500,000 Btu/hr 10%

Natural Draft Oil-Fired Hot Water Commercial Packaged Boiler >2,500,000 Btu/hr 13%

Mechanical Draft Gas-Fired Hot Water Commercial Packaged Boiler ≥300,000 Btu/hr and 

≤2,500,000 Btu/hr 50%

Mechanical Draft Gas-Fired Hot Water Commercial Packaged Boiler >2,500,000 Btu/hr 71%

Mechanical Draft Oil-Fired Hot Water Commercial Packaged Boiler ≥300,000 Btu/hr and 

≤2,500,000 Btu/hr 39%

Mechanical Draft Oil-Fired Hot Water Commercial Packaged Boiler >2,500,000 Btu/hr 24%

7.3 COMMERCIAL PACKAGED BOILER ENERGY CONSUMPTION

To calculate the energy use of commercial packaged boilers in each equipment classes, 

DOE determines the energy consumption associated with space heating, water heating and 

electricity use during periods of space and water heating. For the space-heating energy 

consumption determination, DOE estimates the input capacity and burner operating hours of the 

existing boiler using the building heating energy consumption and boiler characteristics. For the 

water heating energy consumption determination, DOE identifies the building water heating 

energy consumption and the recovery efficiency of the existing boiler. The electricity

consumption is determined using the burner operating hours associated with space and water 

heating and individual electrical measurements of all electrical components. The sum of the 

space heating, water heating, and electrical energy consumption represents the estimated annual 

energy use of a sampled boiler. Additional details used for determining the total energy use can 

be found in the following sections.

The calculation for the determination of the total energy use is as follows:
7-8

Ennnnn UU ttttt = FF F SS + FF F W + E E ttttt

Eq. 7.1

Where:

FF F SS = total fuel consumption as a result of space heating loads,

FF F W = total fuel consumption as a result of water heating loads, and

E E ttttt = electrical consumption of all electrical components.

7.3.2 Space-Heating Fuel Consumption

The space-heating energy use methodology is illustrated by Figure 7.3.1.

Figure 7.3.1 Space-Heating Energy Use Methodology

DOE calculated the annual space-heating fuel consumption (FuelUseSH) for each boiler 

using the following formula:

FF F SS = BBBSS × Qii

Eq. 7.2

Where:

BOHSH = full-load space-heating burner operating hours (hr/yr), and

Qin = input capacity of existing boiler (kBtu/hr).

Efficiency Existing 

+ Secondary Equip. 

Adjustment 

*

CBECS or RECS

Energy Use

HDD Adjust. + 

Building Shell Adjust. 

**

* Existing Equipment Adjustment

** Heating Load Adjustment to 2019

Heating Load

CE to TE Adjust. when 

Applicable 

+ Return Water Temp. 

Adjust. (cond. ≠ non-cond.)

+ Part Load/Cycling Adjust.

Proposed 

Rated 

Efficiency

Input Capacity 

(based on sample)

New Energy Use

Burner

Operating Hours
7-9

DOE derives the BOH from the building-heating load served by a single boiler. The 

building-heating load is determined from annual fuel consumption for heating reported in 

CBECS and RECS based on the efficiency of the existing boiler.

7.3.2.2 Determination of Space-Heating Burner Operating Hours (BOHSH)

DOE calculates space-heating burner operating hours at full-load for a boiler as:

BBBSS = BBBb bb

Qii × T r, a

Eq. 7.3

Where:

TErated, adj = rated thermal efficiency proposed, adjusted to account for the conversion between 

combustion efficiency and thermal efficiency when applicable,

g part-load operation (for

multi-stage equipment) or cycling losses (for single-stage equipment), and return water 

temperatureh (see appendix 7-B for more detail),

Qin = as defined in Eq. 7.2, and

BHLboiler = building heating load served by a single boiler operating at full load (kBtu/yr).

See appendix 7-B for more details on the adjustments made to rated thermal efficiency.

The annual building-heating load (BHLboiler) is the total amount of heat output from the 

boiler that the building needs during the heating season.iDOE determined BHLtotal for each 

sampled building or housing unit, based on the efficiency of the existing boiler, using the 

following calculation:

BBBb bb = QYY × T e, a

Eq. 7.4

Where:

QYR = annual fuel consumption for space heating based on CBECS 2003 or RECS 2009 

(kBtu/yr),

TEex,adj = thermal efficiency of the existing boiler (TEex) adjusted for the same considerations as 

in the case of TErated, adj.

Both CBECS 2003 and RECS 2009 and report space-heating energy use (QYR) for each of 

the sampled buildings. See appendix 7-B for more details about the derivation of the BHL.

 g DOE determines a relationship between the combustion efficiency and thermal efficiency for the four equipment 

classes using combustion efficiency as the efficiency metric. See appendix 7-B for more details. h Return water temperature represents the average annual return water temperature for the different space heating 

applications.

i

BHL is the load served by a single boiler. DOE assumes that 50 percent of buildings are served by two boilers that 

share the load equally, while the remaining 50 percent are served by one boiler.
7-10

The efficiency of the existing boiler (TEex) is determined by matching historical 

efficiency data to the distribution of boiler age for CBECS 2003 buildings or reported age of the 

boiler in RECS 2009.

j

The efficiency of the existing boiler is adjusted to account for differences 

in average return water temperature (RWT) and cycling losses. Appendix 7-B provides 

additional detail regarding the derivation of the adjustment values.

Appendix 7B section 7.2.1 provides the adjustments to the efficiency of the existing 

boiler based on return water temperature (RWT) application types, cycling losses, and part-load 

operation. High RWT is applied to all non-condensing boiler installations. For condensing boiler 

installations, low RWT is applied to all boilers in the new construction market, 25 percent of

replacement boilers in buildings built after 1990, and 5 percent of replacement boilers in 

buildings built before 1990. DOE assumes that all other condensing boiler installations are high 

RWT applications. The efficiency adjustment for low and high RWT is dependent on climate.

DOE adjusts the efficiency of two-stage and modulating condensing boilers to account 

for increased efficiency at part-load operation. In addition, for non-condensing boilers, DOE 

accounts for the decrease in efficiency due to cycling. See appendix 7-B for the adjustment 

factors used for RWT, part-load operation, and cycling by climate zone.

DOE adjusts the BHL to reflect the expectation that the buildings in 2019 will have a 

somewhat different BHL than the buildings in the CBECS 2003 and RECS 2009 building

sample. The adjustment involves multiplying the calculated BHL for each CBECS 2003 or 

RECS 2009 building by the building shell efficiency index from AEO 2014.

k This factor differs 

for commercial and residential buildings as well as new construction and replacement buildings. 

The factor in the analysis for commercial buildings ranges from 0.75 to 0.98 for replacements 

(depending on building type) and from 0.84 to 1.00 for new construction, while for residential 

buildings, it ranges from 0.79 to 0.97 for replacements and from 0.91 to 1.03 for new 

construction. This means that buildings on average will have lower or slightly lower space 

heating load compared to commercial buildings in 2003 or residential buildings in 2009.

DOE also adjusts the BHLTOTAL calculated using heating degree days reported in CBECS 

2003 and RECS 2009 for each building, National Oceanic and Atmospheric Administration 

(NOAA) data by region to reflect historical average climate conditions.

7 The adjustment factors

are calculated using the following equation:

 j

CBECS 2003 does not report the age of the equipment, so DOE created a uniform distribution to estimate the age 

of the equipment.

k The building shell efficiency index sets the heating load value at 1.00 for an average commercial building in 2003

and an average residential building (by type) in 2009 in each census division. The current analysis is based on 

information from the National Energy Modeling System (NEMS) simulation performed for EIA’s Annual Energy 

Outlook (AEO 20135 for commercial buildings and AEO 20146 for residential buildings)._ENREF_4 See 

appendix 7-B for more details.
7-11

AAjf f a a ccccccc=

HH10yr aa

HHb

Eq. 7.5

Where:

HDDbldg= HDD in 2003 or 2009 for commercial or residential buildings (respectively), for the 

specific region where the building is located, and

HDD10_yr_avg = 10-year average HDD (2004–2013) based on NOAA data for the specific region

where the building is located.l

The adjustment factors for commercial buildings range from 0.94 to 0.97 (i.e., 2003 was 

in general colder than the 10-year average), while the residential sample factors range from 0.94 

to 1.05.

DOE understands that some of the sampled buildings use multiple heating appliances

with the same fuel as the boiler(s), such as a central furnace, wall furnace, room heater, stove, or 

fireplace. Therefore, DOE adjusts the calculated BHL when necessary to reflect the use of 

secondary heating equipment using the same fuel as the boiler(s). The adjustment factors are 

calculated using reported survey information from both CBECS 2003 and RECS 2009 regarding 

the fraction of heating that is met by different heating equipment. See appendix 7-B for more 

details.

7.3.2.3 Determination of Equipment Sizing

To support the calculation of space-heating energy use, DOE establishes a methodology 

for deriving the boiler input capacities of each of the sampled buildings. The determination of the 

input capacity of the boiler accounts for the adjusted heating load of the building (adjusted with 

the considerations described above), the efficiency of the existing boiler, and the oversize factor. 

The boiler input capacity is assumed to be the same for the existing boiler and the boiler being 

considered under the standard.

Qii = AA A A AA AAA

T e e

× O OO

Eq. 7.6

Where:

AdjustedHeatLoad = estimated building heat loss adjusted for building weather location (kBtu/h)

(see appendix 7-B),

TEexisting = TE of the existing boiler for each product class (see appendix 7-B), and,

OversizeFactor = 1.1, based on input from consultants on typical sizing practices.

 l

The last 10-year average is used to normalize the HDD values, which is similar to what is done in AEO 2014.
7-12

DOE calculates the adjusted heating load for each sample building or housing unit based 

on the applicable building characteristics and outdoor conditions derived from the CBECS and 

RECS data. 

DOE develops a methodology to derive the total heat loss of the building (i.e., adjusted 

heating load). Appendix 7-B presents the variables used as well as further information about the 

building characteristics and heating load values used for the sizing of boiler equipment.

7.3.3 Water-Heating Energy Consumption

Commercial packaged boilers are often used to provide hot water in addition to space 

heating. The most common means of doing so are through an indirect water heater, tankless coil, 

or as an integrated part of the boiler.

CBECS 2003 and RECS 2009 do not provide information about when a commercial 

packaged boiler is used to provide hot water. Where CBECS or RECS report that the buildings 

used the same fuel for both space and water heating, DOE assumes that 50 percent of the 

installations also use boilers for water heating.

To calculate the water-heating energy use, DOE calculates the boiler fuel use for water 

heating based on the following equation:

FF F W = W

T − AAjF W

Eq. 7.7

Where:

WHL = water heating energy use based on CBECS 2003 or RECS 2009,

TE = TE of the selected efficiency level, and

Adj_FactorWH = adjustment factor to take into account the difference between TE and recovery 

efficiency for water heating, which is assumed to be 4.5 percent TE for non-condensing units 

and 2.25 percent TE for condensing units. A heat loss of 0.5 kBtu/h was considered for 

indirect water heaters.

DOE uses the following equation to calculate the water heating load (WHL):

W = QYY, × (T e − AAjF W )

Eq. 7.8

Where:

QYR,HW = annual fuel consumption for water heating based on CBECS 2003 or RECS 2009

(kBtu/yr),

TEex = TE of the existing boiler (see appendix 7-B), and

Adj_FactorWH = as defined previously.
7-13

7.3.4 Electricity Consumption

DOE calculates boiler electricity consumption for the circulating pump, the draft inducer

(in the case of mechanical draft equipment), and the igniter. The circulating pump moves water 

through the building whenever the boiler burner is on (adjusted for delay times between burner 

and pump operation). If the boiler provides water heating, the circulating pump also operates in 

the cooling season (summer) when there is a call for water heating. In the case of modulating 

condensing boilers, to accommodate for lower firing rates, the inducer provides lower

combustion airflow to regulate the excess air in the combustion process. 

DOE also takes into account the electricity consumption of auxiliary equipment such as 

condensate pumps, which are sometimes installed with higher efficiency equipment. If a building 

requires a condensate pump, DOE assumes that consumes 60 watts and operates at the same time 

as the burner. Details of how DOE determines whether a building required a condensate pump 

can be found in appendix 8-D.

DOE calculates the electricity consumption as:m

E E ttttt = BBBSS × AA BB × E EE E + E E W × E EE E

+S S × S S

Eq. 7.3.1

Where:

BOHSH = as defined in Eq. 7.2,

AdjBOH = adjustment factor that takes into account part-load operation (for condensing units 

only),

ElecPower = power of multiple electrical components required during boiler operation, (kW),

ElecBOHWH = assumed to be 20 percent of BOHSH adjusted for part-load operation,

StdbyPower = total standby power of the equipment, and

StdbyHrs = standby hours, taking into account periods of water heating in the summer 

Further details for calculating electricity consumption appear in appendix 7-B.

7.4 SUMMARY OF ENERGY USE RESULTS

This section presents the average annual energy use and the average energy savings for 

each considered energy efficiency level compared to the baseline energy efficiency for each 

commercial packaged boiler equipment class. The results reflect energy use in both the 

commercial and residential samples. The LCC and PBP analyses use the results calculated for 

each sample building. Negative results indicate that energy use increases.

 m For two-stage and modulating equipment, this formula includes parameters for the operation at full, modulating, 

and reduced load. See appendix 7-B.
7-14

Table 7.4.1 Average Annual Energy Consumption and Savings for Commercial

Packaged Boilers

EL Design Option

Annual Fuel Use

Annual Electricity 

Consumption of Auxiliary 

Components 

Total Savings Total Savings

MMBtu/yr MMBtu/yr kWh/yr kWh/yr

Natural Draft Gas-Fired Hot Water Commercial Packaged Boiler ≥300,000 Btu/hr and ≤2,500,000 

Btu/hr

0 80% TE - Baseline 830.1 - 341.5 -

1 81% TE 819.7 10.4 337.3 4.2

2 82% TE 809.5 20.6 333.2 8.4

3 85% TE - Max Tech 780.5 49.6 321.4 20.2

Natural Draft Gas-Fired Hot Water Commercial Packaged Boiler >2,500,000 Btu/hr

0 82% CE - Baseline 3825.8 - 885.7 -

1 83% CE 3771.8 54.0 873.3 12.4

2 84% CE - Max Tech 3719.4 106.4 861.3 24.4

Natural Draft Oil-Fired Hot Water Commercial Packaged Boiler ≥300,000 Btu/hr and ≤2,500,000 

Btu/hr

0 82% TE - Baseline 597.9 - 309.0 -

1 83% TE 590.3 7.6 305.0 3.9

2 85% TE 575.7 22.2 297.5 11.5

3 87% TE - Max Tech 561.8 36.1 290.3 18.7

Natural Draft Oil-Fired Hot Water Commercial Packaged Boiler >2,500,000 Btu/hr

0 84% CE - Baseline 2298.1 - 685.1 -

1 85% CE 2269.7 28.4 676.7 8.4

2 86% CE - Max Tech 2241.9 56.1 668.5 16.7

Natural Draft Gas-Fired Steam Commercial Packaged Boiler ≥300,000 Btu/hr and ≤2,500,000 Btu/hr

0 77% TE - Baseline 747.6 - 330.0 -

1 79% TE 727.8 19.8 321.3 8.7

2 80% TE - Max Tech 718.3 29.3 317.1 12.9

Natural Draft Gas-Fired Steam Commercial Packaged Boiler >2,500,000 Btu/hr

0 77% TE - Baseline 4051.9 - 1007.9 -

1 79% TE 3942.5 109.4 981.0 27.0

2 80% TE 3890.0 161.8 968.0 39.9

3 81% TE - Max Tech 3838.9 213.0 955.4 52.5

Natural Draft Oil-Fired Steam Commercial Packaged Boiler ≥300,000 Btu/hr and ≤2,500,000 Btu/hr

0 81% TE - Baseline 838.9 - 395.1 -

1 82% TE 828.1 10.8 390.0 5.1

2 83% TE - Max Tech 817.6 21.3 385.1 10.0

Natural Draft Oil-Fired Steam Commercial Packaged Boiler >2,500,000 Btu/hr

0 81% TE - Baseline 2924.2 - 859.9 -

1 82% TE 2886.5 37.8 848.8 11.1

2 83% TE 2849.7 74.5 838.0 21.8

3 85% TE - Max Tech 2778.8 145.4 817.3 42.6

Mechanical Draft Gas-Fired Hot Water Commercial Packaged Boiler ≥300,000 Btu/hr and ≤2,500,000 

Btu/hr

0 80% TE - Baseline 938.8 - 746.2 -

1 83% TE 903.7 35.1 720.3 25.9

2 85% TE 881.8 57.0 704.1 42.1
7-15

3 87% TE 860.9 77.9 688.7 57.5

4 92% TE 824.5 114.3 990.3 -244.1

5 95% TE 797.5 141.3 959.7 -213.5

6 98% TE - Max Tech 772.2 166.5 931.1 -184.9

Mechanical Draft Gas-Fired Hot Water Commercial Packaged Boiler >2,500,000 Btu/hr

0 82% CE - Baseline 3698.9 - 1305.8 -

1 84% CE 3595.9 103.0 1271.1 34.7

2 86% CE 3498.5 200.4 1238.3 67.5

3 94% CE 3182.0 517.0 1662.0 -356.2

4 97% CE - Max Tech 3068.6 630.3 1604.7 -298.9

Mechanical Draft Oil-Fired Hot Water Commercial Packaged Boiler ≥300,000 Btu/hr and ≤2,500,000 

Btu/hr

0 82% TE - Baseline 680.2 - 685.7 -

1 83% TE 671.6 8.6 677.6 8.1

2 84% TE 663.1 17.1 669.7 16.0

3 87% TE 639.1 41.1 647.1 38.6

4 98% TE - Max Tech 573.8 106.4 857.8 -172.1

Mechanical Draft Oil-Fired Hot Water Commercial Packaged Boiler >2,500,000 Btu/hr

0 84% CE - Baseline 2240.9 - 1059.9 -

1 86% CE 2186.1 54.7 1035.2 24.7

2 88% CE 2134.0 106.8 1011.7 48.2

3 97% CE - Max Tech 1976.1 264.7 1342.4 -282.5

Mechanical Draft Gas-Fired Steam Commercial Packaged Boiler ≥300,000 Btu/hr and ≤2,500,000 

Btu/hr

0 79% TE - Baseline 752.4 - 672.7 -

1 80% TE 742.7 9.7 664.6 8.1

2 81% TE 733.3 19.1 656.7 16.0

3 83% TE - Max Tech 715.2 37.3 641.5 31.2

Mechanical Draft Gas-Fired Steam Commercial Packaged Boiler >2,500,000 Btu/hr

0 79% TE - Baseline 3925.3 - 1524.2 -

1 80% TE 3873.0 52.3 1504.7 19.5

2 83% TE - Max Tech 3724.3 201.0 1449.1 75.1

Mechanical Draft Oil-Fired Steam Commercial Packaged Boiler ≥300,000 Btu/hr and ≤2,500,000 

Btu/hr

0 81% TE - Baseline 830.1 - 785.7 -

1 83% TE 809.0 21.1 766.9 18.8

2 84% TE 798.9 31.2 757.9 27.8

3 86% TE - Max Tech 779.3 50.8 740.4 45.2

Mechanical Draft Oil-Fired Steam Commercial Packaged Boiler >2,500,000 Btu/hr

0 81% TE - Baseline 2925.6 - 1334.2 -

1 83% TE 2851.0 74.6 1301.5 32.7

2 86% TE - Max Tech 2746.0 179.6 1255.5 78.8
7-16

REFERENCES

1. U.S. Department of Energy: Energy Information Administration, Residential Energy 

Consumption Survey: 2009 RECS Survey Data, 2013. (Last accessed March, 2014.) 

<http://www.eia.gov/consumption/residential/data/2009/>

2. U.S. Department of Energy: Energy Information Administration, Commercial Buildings 

Energy Consumption Survey, 2003. (Last accessed November, 2013.) 

<http://www.eia.gov/consumption/commercial/data/2003/index.cfm?view=microdata>

3. Air Conditioning Heating and Refrigeration Institute, Directory of Certified Product 

Performance for Commercial Boilers, 2014. (Last accessed 5/26/2014, 2014.) 

<http://www.ahridirectory.org/ahridirectory/pages/home.aspx>

4. Air Conditioning Heating and Refrigeration Institute, Directory of Certified Product 

Performance for Residential Boilers, 2013.

<http://www.ahridirectory.org/ahridirectory/pages/home.aspx>

5. U.S. Department of Energy-Energy Information Administration, Annual Energy Outlook 

2013 with Projections to 2040, 2013. Washington, DC. 

<http://www.eia.gov/forecasts/aeo/>

6. U.S. Department of Energy-Energy Information Administration, Annual Energy Outlook 

2014 with Projections to 2040, 2014. Washington, DC. 

<http://www.eia.gov/forecasts/aeo/>

7. National Oceanic and Atmospheric Administration, NNDC Climate Data Online, (Last 

accessed March 15, 2013.) <http://www7.ncdc.noaa.gov/CDO/CDODivisionalSelect.jsp>